The present invention generally relates to filter devices for filtering particulate matter from a water stream used in irrigation systems. More particularly, the present invention relates to a water filter installed down stream of a control valve and adapted for automatic removal of accumulated particulate matter therefrom in response to cyclic on/off supply of the water stream.
Water filters are used in a wide range of different applications to collect and remove particulate matter from a water flow stream. U.S. Pat. No. 4,360,037 to Kendall, discloses a self-cleaning filter assembly for use in solenoid-actuated valves having fluid pressure-operated diaphragms that control the opening and closing of the valve. Such solenoid-actuated valves includes small passageways leading to a control chamber, requiring the filtering of the water control stream to prevent the blockage of the small passageways. The Kendal device utilizes a plurality of rigid scraper blades urged under spring force into scraping contact with an upstream surface of the filter each time the valve is opened or closed. However, the Kendall device described above filtered only the control stream which served to actuate the valve, leaving the irrigation stream untreated.
Water filters are also employed in irrigation systems to filter out fine particulate and debris which may be present in the water supply, to prevent such particulate matter from passing to sprinkler heads or low-flow emitter devices, such as drip hoses, where such particulate matter can obstruct or otherwise interfere with the delivery of the irrigation water at selected rates to surrounding vegetation. Such filters have typically included a filter medium designed to collect particulate of a target fine mesh size wherein pressure drop across the filter medium is directly proportional to the quantity of the particulate collected thereon. Since an excessive pressure drop across the filter medium can significantly reduce water flow and thereby adversely impact the performance of the irrigation system, the filter medium must be periodically cleaned and the accumulated particulate removed.
In the past, changing or cleaning of the filter medium has generally required manual intervention to access and expose the filter medium. Brushing devices have been devised which contact the filter medium to dislodge the particulate matter from the filter medium so that it can discharged to a disposal area. However, such previously used devices have required manual operation or external additional mechanical power and controls. Systems have been devised whereby the filter medium is back washed and the particulate matter discharged out of the system, however, these systems have been found to be excessively complicated, requiring additional equipment, expense, and maintenance labor.
Accordingly, there is a continuing need for a self-cleaning water filter device which is placed down stream from a control valve and which filters the irrigation water stream. The present invention fulfills this need and provides other related advantages.
The present invention resides in a self-cleaning water filter assembly which automatically cleans and back washes a filter thereof with each on and off cycle of an upstream control valve.
The water filter assembly generally comprises a body having inlet and outlet portions through which water can flow. An elongated filter housing portion is disposed between the inlet and the outlet portions and defines a filter housing cavity having top and bottom ends. In a particularly preferred embodiment, the housing is removably attached to the body. A generally cylindrical seat is formed at the junction between the inlet and the top end of the cavity. A flush opening is formed through the bottom end of the cavity for discharging particulate flow into the atmosphere.
A generally cylindrical filter is disposed concentrically within the filter housing cavity between the inlet and the outlet so that water from the inlet flows from an inner surface of the filter to an outer surface of the filter and then to the outlet.
A generally cylindrical and elongated piston is disposed concentrically within the filter and is axially movable relative to the filter between upper and lower positions within the cavity in response to the pressure of pressurized water at the inlet. The piston has a generally cylindrical sidewall interconnecting upper and lower ends thereof. An axially directed bore extends internally from adjacent the upper end to the lower end of the piston. At least one, and preferably two scrapers are attached to the piston adjacent to the upper end thereof so as to project radially outwardly of the piston sidewall into frictional engagement with the inner surface of the filter to dislodge particulate matter as the piston is moved. Typically, the scrapers are generally cylindrical and comprised of a resiliently flexible material. At least one aperture extends adjacent the upper end of the piston between the scrapers and through the sidewall to the piston bore to channel the dislodged particulate matter through the bore to the flush openings of the housing. A vertically oriented aperture may be formed through a top surface of the piston and into the bore to direct particulate back wash above the piston into the bore.
A spring concentrically surrounds the piston and is supported at a lower end by the housing, and at an upper end by the piston to bias the piston toward the upper position within the cavity so that the piston engages the valve seat in the absence of water pressure.
A seal projects upwardly from the bottom end of the housing cavity and is adapted to seal the piston bore when the piston is in the lower position, resulting in the blockage of particulate flow to the housing flush openings.
When the water is turned off, the spring biases the piston towards its upward position within the cavity, resulting in the dislodgement of particulate matter and debris from the inner surface of the filter. The residual water pressure flushes this debris through the apertures of the piston, into the piston bore, and out of the flush openings of the housing cavity. Thus, the filter is cleanined with each on and off cycle of the irrigation system, preventing filter clogging.
Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.